The present invention relates to a scroll fluid machine such as a scroll compressor or a scroll vacuum pump.
A scroll fluid machine comprises a driving shaft driven by an electric motor and comprising an eccentric axial portion at one end; an orbiting scroll rotatably mounted around the eccentric axial portion via a bearing and having an orbiting wrap on an orbiting end plate; and a fixed scroll having a fixed wrap on a fixed end plate. The orbiting wrap engages with the fixed wrap to form a sealed chamber. A self-rotation-preventing device is provided to prevent the orbiting scroll from rotating on its own axis.
The orbiting scroll is eccentrically revolved with the eccentric axial portion of the driving shaft and self-rotation-preventing device. The sealed chamber is gradually decreased in volume toward the center to allow fluid sucked from the outer circumference to be compressed, or is gradually increased away from the center to allow fluid sucked from the center to be decompressed and discharged from the outer circumference.
In such a scroll fluid machine, thermal load increases with compression and expansion. Especially, heat significantly affects a rotary part or a bearing rotatably supporting the eccentric axial portion of the orbiting scroll. JP63-43427Y2 discloses that an axial fan is provided in the housing of the scroll fluid machine to allow external air taken in from the inlet to blow into the rear surface of the sealed or compression chamber and to be discharged from the outlet to the housing.
The scroll fluid machine can transfer external air sucked from the inlet to the rear surface of the sealed chamber and a bearing for the driving shaft close to the rear wall of the housing, but it cannot flow air to a bearing for the eccentric axial portion which cannot effectively be cooled.